Google de-ranks many file-sharing sites and pirated content. Additionally, if the creator has issued DMCA takedowns, those PDFs disappear from search results. You’re better off searching specific fan communities or, ideally, the official source.
It depends on the series length. Some Miss Rita runs span 5+ years. Most creators sell “Volumes” (e.g., Vol. 1 = Episodes 1–30). Few sell a “Complete Series” PDF until the comic ends. miss rita comics episodes pdf file full